Battery management system for transmitting secondary protection signal and diagnosis signal using a small number of insulation elements

ABSTRACT

Disclosed is a battery management system for transmitting a secondary protection signal and a diagnosis signal using a small number of insulation elements. N battery management units included in the battery management system transmit at least two pieces of data via one communication line through time division. N data signals transmitted from the N battery management units are transmitted in a sequential order or are mixed to one signal and transmitted to an external device.

TECHNICAL FIELD

The present disclosure relates to a battery management system (BMS) fortransmitting a secondary protection signal and a diagnosis signal, andmore particularly, to a BMS for transmitting a secondary protectionsignal and a diagnosis signal using a small number of insulationelements.

The present application claims priority to Korean Patent Application No.10-2013-0127905 filed in the Republic of Korea on Oct. 25, 2013, thedisclosures of which are incorporated herein by reference.

BACKGROUND ART

Due to its characteristics of being easily applicable to variousproducts and electrical characteristics such as a high energy density, asecondary battery is not only commonly applied to a portable device, butuniversally applied to an electric vehicle (EV), a hybrid electricvehicle (HEV), or an energy storage system that is propelled by anelectric motor. This secondary battery is gaining attention for itsprimary advantage of remarkably reducing the use of fossil fuels and notgenerating by-products from the use of energy, making it a neweco-friendly and energy efficient source of energy.

A secondary battery can be charged and discharged repeatedly byelectrochemical reactions between elements including a cathode currentcollector, an anode current collector, a separator, an active material,an electrolyte solution, and the like. By way of example, a lithiumpolymer secondary battery being widely used has an operating voltage ina range of about 3.7V to about 4.2V. Accordingly, to obtain a high powerbattery pack for use in an electric vehicle, a plurality of unitsecondary battery cells are connected in series to construct a batterypack.

In addition to this basic structure, the battery pack further includes abattery management system (BMS) to monitor and control a state of asecondary battery by applying an algorithm for control of power supplyto a driving load such as a motor, measurement of electricalcharacteristic values such as current or voltage, charge/dischargecontrol, voltage equalization control, state of charge (SOC) estimation,and the like.

Recently, with the increasing need for a high-capacity structure as wellas utilization as an energy storage source, the demand for a batterypack of a multi-module structure in which a plurality of battery modulesincluding a plurality of secondary battery cells are assembled, is alsoincreasing.

Because the battery pack of the multi-module structure includes aplurality of secondary battery cells, there is a limitation incontrolling the charge/discharge state of all the secondary batterycells or the plurality of battery modules using a single BMS.Accordingly, a recent technology has been introduced in which a batterymanagement unit (BMU) is provided to each battery module included in thebattery pack, the BMUs are designated as a slave unit, and a master BMSis additionally provided to control the slave units, such that thecharge and discharge of each battery module is controlled in amaster-slave mode.

FIG. 1 is a block diagram schematically illustrating a connected stateof an external device 10 and a BMS 100 according to a related art.

Referring to FIG. 1, the BMS 100 including eight slave units 210 and onemaster unit 211 is provided. Also, the BMS 100 is connected to a batterypack 110 including a plurality of secondary battery cells 111 connectedin series. The BMS 100 controls the charge and discharge of the batterypack 110, and further, measures the voltage of the secondary batterycells 111 included in the battery pack 110. The BMS 100 receives acontrol signal associated with charge and discharge from the externaldevice 10, and transmits data associated with a state of the secondarybattery cells 111. However, as described in the foregoing, because thebattery pack 110 includes the plurality of unit secondary battery cellsconnected in series to obtain a high power battery pack for use inelectric vehicles and the like, the external device 10 needs to beelectrically separated from the BMS 100 to prevent the external device10 from being damaged due to a high voltage.

To this end, a photo coupler capable of transmitting and receiving anelectrical signal while electrically separating the external device 10from the BMS 100 is connected and used.

The photo coupler is also called an opto-coupler. The photo couplercorresponds to a switching element including a light emitting source(input) and a light detector (output). Generally, an infrared lightemitting diode (LED) is used as the light emitting source, and aphotodiode or a phototransistor which turns on in response to light isused as the light detector. Thus, when an electric current flows to theinput side, the light emitting source emits light, and then the outputside element, i.e., the photodiode or phototransistor turns on. That is,the photo coupler is a switching element designed to turn on and off bylight, not electrical coupling.

When the photo coupler is used in connecting the external device 10 tothe BMS 100, an advantage is that the external device 10 may beelectrically separated from the BMS 100. Also, a reverse current causinga high voltage current from the battery pack 110 to be inputted to theexternal device 10 side may be prevented while transmitting a datasignal, and influence of electromagnetic waves generating during chargeand discharge of the battery pack 110 may be lessened.

When the BMS operates in a master-slave mode, to provide a precautionagainst a failure that may occur in the master unit 211, the slave units210 may be configured to directly deliver information associated withthe secondary battery cells 111 to the external device 10. FIG. 1illustrates three types of data each slave unit 210 transmits to theexternal device 10 to take precaution against a failure in the masterunit 211.

A ‘2nd_PROT’ signal transmitted from the slave unit 210 refers to asignal representing that the secondary battery cells 111 areover-charged more than a preset voltage. A ‘Under V PROT’ signaltransmitted from the slave unit 210 refers to a signal representing thatthe secondary battery cells 111 are over-discharged less than a presetvoltage. A ‘Diag’ signal transmitted from the slave unit 210 refers to asignal representing whether an abnormality has occurred or not throughself-diagnosis of the slave unit 210.

In this way, each slave unit 210 transmits three types of data to theexternal device 10, and when a number of such slave units 210 is eight,a total number of photo couplers needed to connect the external device10 to the slave units 210 is twenty four. The photo coupler is a morecostly element than other electric and electronic elements, which is afactor of increasing a manufacturing cost of the BMS.

Therefore, there is a need for studies on a BMS that may transmit asignal from the slave units 210 included in the BMS 10 to the externaldevice 10 while maintaining insulation between the BMS 100 and theexternal device 10.

DISCLOSURE Technical Problem

The present disclosure is designed to solve the problem of the relatedart, and therefore the present disclosure is directed to providing abattery management system (BMS) for transmitting a secondary protectionsignal and a diagnosis signal using a small number of insulationelements.

Technical Solution

To achieve the object, a battery management system according to thepresent disclosure is a system that manages a battery pack, and includesN battery management units configured to manage secondary batteriesincluded in the battery pack, in which N is a natural number greaterthan or equal to 2, N communication lines electrically connected to eachbattery management unit to transmit data to an external device whichcontrols the battery management system, and N insulation elementsconnected between the external control device and the battery managementsystem and configured to transmit a signal while electrically separatingthe external device from the N communication lines, wherein each batterymanagement unit transmits at least two pieces of data through timedivision.

To achieve the object, a battery management system according to thepresent disclosure is a system that manages a battery pack, and includesN battery management units configured to manage secondary batteriesincluded in the battery pack, in which N is a natural number greaterthan or equal to 2, N communication lines electrically connected to eachbattery management unit to transmit data to an external device whichcontrols the battery management system, an insulation element configuredto transmit a signal while electrically separating the external controldevice from the battery management system, a switch configured toselectively connect any one of the N communication lines to theinsulation element by a control signal, and a switch controllerconfigured to output a control signal to the switch, wherein eachbattery management unit transmits at least two pieces of data throughtime division.

To achieve the object, a battery management system according to thepresent disclosure is a system that manages a battery pack, and includesN battery management units configured to manage secondary batteriesincluded in the battery pack, in which N is a natural number greaterthan or equal to 2, N communication lines electrically connected to eachbattery management unit to transmit data to an external device whichcontrols the battery management system, an insulation element configuredto transmit a signal while electrically separating the external controldevice from the battery management system, and a calculator electricallyconnected to the N communication lines to connect any one of the Ncommunication lines to the insulation element, wherein each batterymanagement unit transmits at least two pieces of data through timedivision.

To achieve the object, a battery management system according to thepresent disclosure is a system that manages a battery pack, and includesN battery management units configured to manage secondary batteriesincluded in the battery pack, in which N is a natural number greaterthan or equal to 2, N communication lines electrically connected to eachbattery management unit to transmit data to an external device whichcontrols the battery management system, an insulation element configuredto transmit a signal while electrically separating the external controldevice from the battery management system, and a signal mixerelectrically connected to the N communication lines to mix signalsreceived through the N communication lines, wherein each batterymanagement unit transmits at least two pieces of data through timedivision.

To achieve the object, a battery management system according to thepresent disclosure is a system that manages a battery pack, and includesN battery management units configured to manage secondary batteriesincluded in the battery pack, in which N is a natural number greaterthan or equal to 2, a communication line electrically connected to the Nbattery management units to transmit data to an external device whichcontrols the battery management system, an insulation element configuredto transmit a signal while electrically separating the external controldevice from the battery management system, and a signal mixerelectrically connected to the communication line to mix signals receivedfrom each battery management unit through the communication line,wherein each battery management unit transmits at least two pieces ofdata through time division.

The insulation element according to the present disclosure may be aphoto coupler.

The battery management system according to the present disclosure mayfurther include a level shift electrically connected between eachbattery management unit and the communication line.

According to the battery management system of the present disclosure, inthe battery management system with the switch controller, the switchcontroller may be connected to the external device through theinsulation element, and may be controlled by the external device.

According to the battery management system of the present disclosure, inthe battery management system with the calculator, the calculator may beconnected to the external device through the insulation element, and mayreceive a control signal from the external device.

According to an exemplary embodiment of the present disclosure, eachbattery management unit may transmit at least two pieces of data throughtime division using ADSYNC changing in logic level of a signal at a datatransmission preparation section and a start point of a datatransmission section.

In this instance, the at least two pieces of data included in the datatransmission section of the ADSYNC may have the same width of each data,and a width of data distant from the start point of the datatransmission section may be wider than a width of data close to thestart point. In the latter case, the width of the data distant from thestart point of the data transmission section may be wider by at least 5%than the width of the data close to the start point of the datatransmission section.

Also, a pulse indicating a boundary between the data may be included inthe data transmission section of the ADSYNC.

According to an exemplary embodiment of the present disclosure, the Nbattery management units may further include a synchronization line toestablish an electrical connection for synchronization with adjacentother battery management unit. In this instance, the N batterymanagement units may perform synchronization by ADSYNC.

The N battery management units may respectively output a free-run ADSYNCand may be synchronized to any one of the outputted free-run ADSYNCs,and the N battery management units may be synchronized to a free-runADSYNC with a narrowest width of a data transmission preparation sectionand a narrowest width of an ADSYNC cycle among the free-run ADSYNCsoutputted from the N battery management units.

Advantageous Effects

According to the present disclosure, a battery management system may beconnected to an external device using a small number of insulationelements.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing illustrates a preferred embodiment of thepresent disclosure and together with the foregoing disclosure, serves toprovide further understanding of the technical spirit of the presentdisclosure, and thus, the present disclosure is not construed as beinglimited to the drawing.

FIG. 1 is a block diagram schematically illustrating a connected stateof an external device and a battery management system (BMS) according toa related art.

FIGS. 2 through 6 are block diagrams schematically illustrating anarchitecture of a BMS according to the present disclosure.

FIG. 7 is a waveform diagram illustrating a configuration of ADSYNC.

FIG. 8 is a waveform diagram illustrating free-run ADSYNC outputted froma battery management unit (BMU) according to the present disclosure.

FIG. 9 is a waveform diagram illustrating synchronized free-run ADSYNCaccording to an exemplary embodiment of the present disclosure.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Priorto the description, it should be understood that the terms used in thespecification and the appended claims should not be construed as limitedto general and dictionary meanings, but interpreted based on themeanings and concepts corresponding to technical aspects of the presentdisclosure on the basis of the principle that the inventor is allowed todefine terms appropriately for the best explanation. Therefore, thedescription proposed herein is just a preferable example for the purposeof illustrations only, not intended to limit the scope of thedisclosure, so it should be understood that other equivalents andmodifications could be made thereto without departing from the spiritand scope of the disclosure.

FIGS. 2 through 6 are block diagrams schematically illustratingarchitectures of battery management systems (BMSs) 101˜106 according tothe present disclosure.

Hereinafter, in the description of the BMSs 101˜106 according to thepresent disclosure with reference to FIGS. 2 through 6, it should beunderstood that elements with the same reference numerals representelements performing the same function. Thus, a detailed description ofeach element will be provided later, and the following description ismade based on a difference between each embodiment.

First, a first embodiment according to the present disclosure as shownin FIG. 2 is described. For convenience of understanding, a BMS 101according to the first embodiment of the present disclosure is describedtogether with the BMS 100 according to the related art as shown inFIG. 1. Each battery management unit (BMU) 310 shown in FIG. 2 isconnected with each communication line 330. That is, dissimilar to therelated art, a number of communication lines do not increase with anincreasing number of data to be transmitted. The first embodiment ischaracterized in that each BMU 310 transmits data to the external device10 via each communication line 330. Thus, each BMU 310 transmits atleast two pieces of data through time division.

Also, each BMU 310 is connected to the external device 10 one-to-onethrough an insulator element. In the present disclosure, the insulatorelement may be a photo coupler 320. Since a description of the photocoupler 320 is provided in the foregoing, an overlapping description isomitted herein.

Next, a second embodiment according to the present disclosure as shownin FIG. 3 is described. For convenience of understanding, a BMS 102according to the second embodiment of the present disclosure isdescribed with the BMS 101 according to the first embodiment as shown inFIG. 2.

When comparing the BMS 102 according to the second embodiment of thepresent disclosure to the BMS 101 according to the first embodiment, itcan be seen that one photo coupler (320 depicted at top) is used inconnecting to the BMUs 310 to the external device 10. Also, it can beseen that a switch 350 and a switch controller 340 are included toselectively connect the BMUs 310 to the external device 10. Also, it canbe seen that a photo coupler (320 depicted at bottom) is added tocontrol the switch controller 340. Thus, a total number of photocouplers 320 is two.

The switch 350 serves to selectively connect any one of thecommunication lines 330 to the photo coupler 320 by a control signal ofthe switch controller 340. In this instance, the switch controller 340is connected to the external device 10 through the photo coupler 320,and may be controlled by the external device 10. The BMU 310 having thecommunication line 330 connected to the photo coupler 320 through theswitch 350 may transmit data to the external device 10.

Next, a third embodiment according to the present disclosure as shown inFIG. 4 is described. For convenience of understanding, a BMS 103according to the third embodiment of the present disclosure is describedwith the BMS 102 according to the second embodiment as shown in FIG. 3.

The BMS 103 according to the third embodiment of the present disclosureincludes a calculator 360 to connect the BMUs 310 to the external device10, in place of the switch 350 and the switch controller 340.

The calculator 360 may connect the BMUs 310 to the photo coupler 320freely and selectively. The component of the calculator 360 may beembodied as an electronic circuit module including a logic circuit. Anexample of the electronic circuit module may include anapplication-specific integrated circuit (ASIC). However, the presentdisclosure is not limited thereto.

The BMU 310 having the communication line 330 connected to the photocoupler 320 through the calculator 360 may transmit data to the externaldevice 10.

Next, a fourth embodiment according to the present disclosure as shownin FIG. 5 is described. For convenience of understanding, a BMS 104according to the fourth embodiment of the present disclosure isdescribed with the BMS 103 according to the third embodiment as shown inFIG. 4.

The BMS 104 according to the fourth embodiment of the present disclosuremay include a signal mixer 370 to connect the BMUs 310 to the externaldevice 10, in place of the calculator 360.

The signal mixer 370 refers to a device that mixes N data signals intoone and outputs a single signal. The signal mixer 370 is a well-knownelement to those skilled in the art, and its detailed description isomitted herein.

The signal mixer 370 is electrically connected to each of the Ncommunication lines 330. Also, the signal mixer 370 mixes signalsreceived from each BMU 310 into one. Thus, the signals outputted fromthe N BMUs 310 are mixed into one and transmitted to the external device10.

Next, a fifth embodiment according to the present disclosure as shown inFIG. 6 is described. For convenience of understanding, a BMS 105according to the fifth embodiment of the present disclosure is describedwith the BMS 104 according to the fourth embodiment as shown in FIG. 5.

In the BMS 105 according to the fifth embodiment of the presentdisclosure, it can be seen that each BMU 310 is electrically connectedto the signal mixer 370 through one communication line 330. Thus, thesignal mixer receives the signals outputted from the N BMUs 310 in ssequential order, mixes the signals into one, and transmits a singlesignal to the external device 10.

In the description of the exemplary embodiments according to the presentdisclosure, the photo coupler 320 is illustrated as an elementconnecting the external device 10 to the BMSs 101˜105. The photo coupler320 is an example of an insulation element which electrically separatesthe external device 10 from the BMSs 101˜105 while transmitting asignal. Thus, the scope of the present disclosure is not limited to thephoto coupler 320 presented as an example of an insulation element.

In this instance, the BMSs 101˜105 according to the present disclosuremay further include a level shift 390 electrically connected betweeneach BMU 310 and the communication line 330. The level shift 390 refersto a device that outputs an inputted signal with a potential value of adesired range. The level shift 390 is a known element in the art, andits detailed description is omitted herein.

The BMSs 101˜105 according to the present disclosure include the N BMUs310. The N BMUs 310 manage the secondary batteries 111 included in thebattery pack 110. The management of the secondary batteries 111 includedin the battery pack 110 by the BMUs 310 represents execution of varioustypes of control applicable at the ordinary level, includingcharge/discharge current, measurement of electrical characteristicvalues including voltage or electric current of each secondary battery111, charge/discharge control, voltage equalization control, state ofcharge (SOC) estimation, and the like.

In this instance, the battery pack 110 includes at least one secondarybattery 111, and the secondary battery 111 is not limited to a specifictype. Each secondary battery may include a lithium ion battery, alithium polymer battery, a Ni—Cd battery, a Ni-MH battery, and a Ni—Znbattery, that is rechargeable and needs to consider a charge ordischarge voltage. Also, a number of secondary batteries 111 included inthe battery pack 110 may be variously set based on a required outputvoltage or charge/discharge capacity. However, the present disclosure isnot limited by a type, an output voltage and a charge capacity of thesecondary battery 111, and the like. Also, although FIGS. 2 through 6show an embodiment in which all the secondary batteries 111 areconnected in series, the present disclosure is not limited to aconnection method of the secondary batteries 111.

The BMU 310 according to the present disclosure transmits at least twopieces of data through one communication line 330 dissimilar to therelated art. Thus, the at least two pieces of data are outputted as adata signal through time division. To this end, the BMU 310 according tothe present disclosure may transmit at least two pieces of data throughtime division using ADSYNC that changes in logic level of the signal ata data transmission preparation section and a start point of a datatransmission section.

The ADSYNC is a sort of communication protocol for data transmission andreception between the BMU 310 and the external device 10. That is, theBMU 310 transmits at least two pieces of data by a prescribed method,and the external device 10 receives and reads the at least two pieces ofdata by the prescribed method.

FIG. 7 is a waveform diagram illustrating a configuration of ADSYNC.

One cycle of the ADSYNC consists of a data transmission preparationsection and a data transmission section. To distinguish the datatransmission preparation section from the data transmission section, theADSYNC changes in logic level of the signal at the data transmissionpreparation section and a start point of the data transmission section.The data transmission preparation section allows output as a high logiclevel signal (H), and the data transmission section allows output as alow logic level signal (L). The high logic level may be set to 5V andthe low logic level may be set to 0V, but the present disclosure is notlimited to the example. In this instance, it will be readily appreciatedif the data transmission preparation section illustrated in the drawingis interpreted as a preset minimum width and one cycle is interpreted asa preset minimum width of ADSYNC cycle.

The BMU 310 and the external device 10 synchronized by the ADSYNC maytransmit and receive the collected data within the preset width duringthe data transmission section. From the start point of the datatransmission section illustrated in FIG. 7, ‘2nd_PROT’, ‘Under V PROT’,and ‘Diag’ may be transmitted in a sequential order. Obviously, the datatransmission order may be variously set.

Hereinafter, the ADSYNC cycle represents one cycle of the signalcomposed of the data transmission preparation section and the datatransmission section (ADSYNC cycle=data transmission preparationsection+data transmission section).

The at least two pieces of data included in the data transmissionsection of the ADSYNC may have the same width or different widths fromeach other.

When the at least two pieces of data included in the data transmissionsection of the ADSYNC have different widths from each other, a width ofdata distant from the start point of the data transmission section iswider than a width of data close to the start point of the datatransmission section. For example, the width of data distant from thestart point of the data transmission section is wider by 5% than thewidth of data close to the start point of the data transmission section.

When the data receiving side, i.e., the external device 10 side, or thedata transmitting side 102 detects or transmits a signal using aresistor-capacitor (RC) oscillator, an error of about 5% or more mayoccur between transmission and reception. It is obvious that the errorreduces with the increasing performance of the RC oscillator, but as theperformance becomes higher, the cost of the RC oscillator becomeshigher. Thus, when an attempt is made to transmit at least two pieces ofdata, communication of data is enabled without using a high performanceRC oscillator by increasing a width of each data, for example, by 5%,taking a possible error into account. When the error is −5%˜+5% andtransmission is made with a predetermined width, a number oftransmittable and receivable data is limited to nine or less.

As shown in FIG. 7, it can be seen that data is transmitted with thegradually increasing width of each data. Also, a pulse indicating aboundary between the data may be included in the data transmissionsection of the ADSYNC. In this instance, the increased width of the datamay increase in width when an error expected in a system to be actuallyused is great.

Also, the BMU 310 according to the present disclosure may furtherinclude a synchronization line to establish an electrical connection forsynchronization with an adjacent other BMU. In this instance, the BMU310 performs synchronization by the ADSYNC.

When there is a difference in timing at which each BMU measures thevoltage or conducts self-diagnosis, voltage measurement is performedincorrectly or data obtained by the voltage measurement may not behelpful to the external device 10. Thus, the BMSs 101˜106 are requiredto perform a synchronization operation of all the BMUs 310 and transmitdata.

To this end, a free-run ADSYNC is outputted through the synchronizationline interconnected between the BMUs 310. The free-run ADSYNC as usedherein refers to a preparative signal for synchronization between theBMUs 310.

FIG. 8 is a waveform diagram illustrating the free-run ADSYNCs outputtedfrom the BMUs 310 according to the present disclosure.

Referring to FIG. 8, it can be seen that the free-run ADSYNCs outputtedfrom the BMUs Unit 1 through Unit 8 differ in width of the datatransmission preparation section and width of the ADSYNC cycle. Thefree-run ADSYNCs of each BMU 310 may serve to identify all the BMUs 310through the synchronization line.

In this instance, the BMUs 310 according to the present disclosure aresynchronized to any one of the outputted free-run ADSYNCs.

According to an exemplary embodiment of the present disclosure, the BMUs310 are synchronized to a free-run ADSYNC with a narrowest width of thedata transmission preparation section and a narrowest width of theADSYNC cycle among the free-run ADSYNCs outputted form the plurality ofBMUs 310.

FIG. 9 is a waveform diagram illustrating the synchronized free-runADSYNCs according to an exemplary embodiment of the present disclosure.

Referring to FIGS. 8 and 9 together, it can be seen in FIG. 8 that thewidth of the data transmission preparation section of Unit 8 isnarrowest and one cycle of free-run ADSYNC is earliest. Thus, accordingto an exemplary embodiment of the present disclosure, it can be seen inFIG. 9 that the free-run ADSYNCs of Unit 1 and Unit 2 are synchronizedwith the free-run ADSYNC of Unit 8.

Subsequently, each BMU 310 measures the voltage of the secondarybatteries 111 or conducts a failure diagnosis according to thesynchronized ADSYNC cycle. Also, when each BMU 310 transmits data to theexternal device 10, the BMUs 310 may determine a transmission order oftheir data.

According to the present disclosure, the BMS and the external device maybe connected using a small number of insulation elements.

Meanwhile, in the description of the present disclosure, it should beunderstood that each element or component of the present disclosureshown in FIGS. 2 through 6 is distinguished logically rather thanphysically.

That is, each element or component corresponds to a logic element orcomponent to realize the technical spirit of the present disclosure, andaccordingly, it should be understood that even though each element orcomponent is integrated or separated, it falls within the scope of thepresent disclosure if a function performed by a logic element orcomponent of the present disclosure can be implemented, and it fallswithin the scope of the present disclosure regardless of whether namesare identical or not if it is an element or component performing anidentical or similar function.

While the present disclosure has been hereinabove described inconnection with a limited number of embodiments and drawings, thepresent disclosure is not limited thereto, and it should be understoodthat various modifications and changes may be made by those skilled inthe art within the technical spirit of the invention and equivalents tothe appended claims.

1. A battery management system for managing a battery pack, comprising:N battery management units configured to manage secondary batteriesincluded in the battery pack, in which N is a natural number greaterthan or equal to 2; N communication lines electrically connected to eachbattery management unit to transmit data to an external device whichcontrols the battery management system; and N insulation elementsconnected between the external control device and the battery managementsystem and configured to transmit a signal while electrically separatingthe external device from the N communication lines, wherein each batterymanagement unit transmits at least two pieces of data through timedivision.
 2. A battery management system for managing a battery pack,comprising: N battery management units configured to manage secondarybatteries included in the battery pack, in which N is a natural numbergreater than or equal to 2; N communication lines electrically connectedto each battery management unit to transmit data to an external devicewhich controls the battery management system; an insulation elementconfigured to transmit a signal while electrically separating theexternal control device from the battery management system; a switchconfigured to selectively connect any one of the N communication linesto the insulation element by a control signal; and a switch controllerconfigured to output a control signal to the switch, wherein eachbattery management unit transmits at least two pieces of data throughtime division.
 3. A battery management system for managing a batterypack, comprising: N battery management units configured to managesecondary batteries included in the battery pack, in which N is anatural number greater than or equal to 2; N communication lineselectrically connected to each battery management unit to transmit datato an external device which controls the battery management system; aninsulation element configured to transmit a signal while electricallyseparating the external control device from the battery managementsystem; and a calculator electrically connected to the N communicationlines to connect any one of the N communication lines to the insulationelement, wherein each battery management unit transmits at least twopieces of data through time division.
 4. A battery management system formanaging a battery pack, comprising: N battery management unitsconfigured to manage secondary batteries included in the battery pack,in which N is a natural number greater than or equal to 2; Ncommunication lines electrically connected to each battery managementunit to transmit data to an external device which controls the batterymanagement system; an insulation element configured to transmit a signalwhile electrically separating the external control device from thebattery management system; and a signal mixer electrically connected tothe N communication lines to mix signals received through the Ncommunication lines, wherein each battery management unit transmits atleast two pieces of data through time division.
 5. A battery managementsystem for managing a battery pack, comprising: N battery managementunits configured to manage secondary batteries included in the batterypack, in which N is a natural number greater than or equal to 2; acommunication line electrically connected to the N battery managementunits to transmit data to an external device which controls the batterymanagement system; an insulation element configured to transmit a signalwhile electrically separating the external control device from thebattery management system; and a signal mixer electrically connected tothe communication line to mix signals received from each batterymanagement unit through the communication line, wherein each batterymanagement unit transmits at least two pieces of data through timedivision.
 6. The battery management system according to claim 1, whereinthe insulation element is a photo coupler.
 7. The battery managementsystem according to claim 1, further comprising: a level shiftelectrically connected between each battery management unit and thecommunication line.
 8. The battery management system according to claim2, wherein the switch controller is connected to the external devicethrough the insulation element, and is controlled by the externaldevice.
 9. The battery management system according to claim 3, whereinthe calculator is connected to the external device through theinsulation element, and receives a control signal from the externaldevice.
 10. The battery management system according to claim 1, whereineach battery management unit transmits at least two pieces of datathrough time division using ADSYNC changing in logic level of a signalat a data transmission preparation section and a start point of a datatransmission section.
 11. The battery management system according toclaim 10, wherein the at least two pieces of data included in the datatransmission section of the ADSYNC have the same width of each data. 12.The battery management system according to claim 10, wherein among theat least two pieces of data included in the data transmission section ofthe ADSYNC, a width of data distant from the start point of the datatransmission section is wider than a width of data close to the startpoint.
 13. The battery management system according to claim 12, whereinthe width of the data distant from the start point of the datatransmission section is wider by at least 5% than the width of the dataclose to the start point of the data transmission section.
 14. Thebattery management system according to claim 10, wherein a pulseindicating a boundary between the data is included in the datatransmission section of the ADSYNC.
 15. The battery management systemaccording to claim 1, wherein the N battery management units furthercomprise a synchronization line to establish an electrical connectionfor synchronization with adjacent other battery management unit.
 16. Thebattery management system according to claim 8, wherein the N batterymanagement units perform synchronization by ADSYNC.
 17. The batterymanagement system according to claim 16, wherein the N batterymanagement units respectively output a free-run ADSYNC and aresynchronized to any one of the outputted free-run ADSYNCs.
 18. Thebattery management system according to claim 17, wherein the N batterymanagement units are synchronized to a free-run ADSYNC with a narrowestwidth of a data transmission preparation section and a narrowest widthof an ADSYNC cycle among the free-run ADSYNCs outputted from the Nbattery management units.